1. Field of the Invention
The present invention relates to a lighting device for a vehicle. More particularly, the present invention relates to an improvement of a lighting device for a vehicle such as a rear combination lamp.
2. Description of the Related Art
Usually, in the lighting device for a vehicle such as a rear combination lamp or a high mount stop lamp, the light of a light source is externally emitted through an outer lens (a designed cover) to obtain a desired light emission. For instance, as shown in FIG. 15(a), a lamp 1102 is disposed inside the outer lens 1101 and a reflector 1103 is provided in the periphery of the lamp 1102 (for instance, see JP-A-2005-123092). In such a structure, the light of the lamp 1102 directly advances or advances forward through the reflector 1103 and is emitted outside through the outer lens 1101.
In the above-described usual lighting device, the outer lens 1101 needs to be connected to a housing 1104 in view of a water-proof structure. Ordinarily, in an edge part (a welding margin) 1105, the outer lens is welded to the housing. When the lighting device having such a structure is observed from a front surface (FIG. 15(b)), the edge part (the welding margin) 1105 is whitened to deteriorate design characteristics. Further, when the lighting device is lighted, the edge part as the welding part does not emit light, which results in the deterioration of the design characteristics.
Also, usually, below-described countermeasures are carried out to the heat generation of a lamp unit in a lighting device for a vehicle. For instance, JP-A-2005-122945 discloses a structure that outside air taken in from a space relative to a housing is directly guided to an LED lamp to cool the LED lamp. Further, JP-A-2003-5121 discloses a structure that a natural convection generated due to a temperature difference of air inside and outside a housing is used to naturally ventilate and cool the housing.
A rear combination lamp having a tail/stop lamp formed integrally with a turn lamp has been employed. Ordinarily, the frequency of use of the tail/stop lamp is high. As compared therewith, the frequency of use of the turn lamp is low. Since a quantity of generated heat is different depending on the difference of the frequency of use, a bias is generated in the distribution of the quantity of generated heat in the housing of the rear combination lamp. When a cooling structure that takes such a bias into consideration is provided, the improvement of a cooling efficiency can be anticipated. However, such a cooling structure is not especially studied.